As reported in Asian Scientist, recent research suggests that children as old as 12 have difficultly telling the difference between genuine and fake sadness from facial expressions.

The study that came out of the Australian National University was published in the journal Frontiers in Psychology.

The study involved children and adults being shown pairs of images showing facial expressions. One depicted an expression of a genuinely-felt emotion and the other depicted the same person faking an expression of the same emotion. Participants were asked to decide which facial expression was ‘only pretend.’

For happy facial expressions, children could distinguish genuine from fake emotions to some extent. However, for sad facial expressions, the child participants had difficulty distinguishing between the two. For both happy and sad faces, children did not do as well as adults.

Researchers said that the results do not mean that children can never tell whether another person is feeling genuinely sad, because they might be able to do this using other information, such as body language or knowing what caused the emotion. But the results do show that, unlike adults, children are poor at doing this just by looking at a person’s face.

Lead researcher Dr. Amy Dawel of the ANU School of Psychology said this may affect children’s ability to build relationships, or leave them open to manipulation. “Being able to tell the difference between genuine and fake facial expressions is crucial to social interaction,” Dawel said. “If children are misinterpreting polite smiles as genuinely happy then they are not picking up important feedback on their own social behavior. They might think that other children find them funny, or want to make friends, when in fact they are only being polite.”

The researchers were also surprised children aged eight to 12 showed no improvement in their ability to identify genuine facial emotion. “There is absolutely no improvement across that period,” Dawel said. “This is a skill that develops quite late—some time during the teenage years. So, we are talking about typical kids entering high school and not yet having developed the subtle skills in face emotion recognition that adults take for granted.”

A genuine smile is also known as a Duchenne smile, named after a French Neurophysiologist from the early 1800s. It occurs when the lip corners move up and the muscle around the eyes (orbicularis oculi) moves as well. Oftentimes you see wrinkles around a person’s eyes. This is often described as a “twinkling” or “sparkling” in the eyes.